I've not used the 68EC000 version myself but looking at the datasheet it looks like A0 is used along with the LDS and UDS lines.
https://www.nxp.com/docs/en/reference-manual/EC000UM.pdfQuote:
During operation in the 16-bit mode, byte operations can occur on either D15–D8 or D7–D0,depending on A0. If A0 is zero, the upper byte is used and UDSB is asserted. If A0 is one,the lower byte is used and LDSB is asserted. For word and long-word operations, A0 is always zero, data bits D15 through D0 are used, and both LDSB and UDSB are asserted.For long-word operations, data is transferred in two bus cycles with A1 indicating which half of the long word is being transferred. The actual order of the long-word halves is instruction and address-mode dependent.
